Some of slot machines as a kind of gaming machines have been known to stop-display a consecutive symbol group (hereinafter also referred to as stack symbol) having plurality of identical or correlated symbols in a row on a symbol display screen for displaying symbols. Stack symbols include those formed of a plurality of symbols in a row and those formed of a large symbol having a size of a plurality of symbols. In the latter case, specifically, symbols displayed at a time on the symbol display screen often constitute a single large symbol.
Players play a game expecting appearance of a stack symbol, because when such a stack symbol is stop-displayed on the symbol display screen, the possibility of winning of a big prize is high. In particular, when the stack symbol is formed as a large symbol, a large symbol displayed in the symbol display region is also visually effective to further increase the degree of expectations of players for occurrence of a stack symbol.